Image quality in thoracic 4D cone-beam CT: A sensitivity analysis of respiratory signal, binning method, reconstruction algorithm, and projection angular spacing
Image quality in thoracic 4D cone-beam CT: A sensitivity analysis of respiratory signal, binning method, reconstruction algorithm, and projection angular spacing
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DOI：
10.1118/1.4868510
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发表时间：
2014-04-01
期刊：
影响因子：
3.8
通讯作者：
Keall, Paul J.
中科院分区：
文献类型：
--
作者：
Shieh, Chun-Chien;Kipritidis, John;Keall, Paul J.
目的：胸部4D锥形束CT（4D-CBCT）广泛应用于图像引导放射治疗（IGRT），呼吸信号、面元方法和重建算法是影响图像质量的3个主要可控因素。以前的研究已经单独调查了这些因素中的每一个，但没有进行综合敏感性分析。此外，投影角间距也是重建中的一个关键因素，但它如何影响图像质量并不明显。这四个因素对图像质量的影响的调查，可以帮助确定最有效的策略，在改善4D-CBCT IGRT.Methods：14个4D-CBCT患者投影数据集与各种呼吸运动功能重建与以下可控因素：（i）呼吸信号（实时位置管理、投影图像强度分析或基准标记跟踪），（ii）分箱方法（相位、位移或等投影密度位移分箱），以及（iii）重建算法[Feldkamp-Davis-Kress（FDK）、McKinnon-Bates（MKB）或自适应最速下降投影到凸集（ASD-POCS）]。使用信噪比（SNR）、对比度噪声比和边缘响应宽度对图像质量进行量化，以评估噪声/条纹和模糊。SNR值也进行了分析，相对于最大值，平均值和均方根误差（RMSE）的投影角间距，以探讨如何投影角间距影响图像quality.Results：呼吸信号的选择被发现对图像质量没有显着影响。在超过一半的情况下，基于位移的分箱被发现与相位分箱相比不太容易产生运动伪影，但被证明遭受大的分箱间图像质量变化和大的投影角间隙。与FDK相比，MKB和ASD-POCS几乎100%的时间都显著改善了图像质量。此外，SNR值被发现随着具有强相关性的投影角间隙的RMSE值的减小而增加（r近似为-0.7），而与所使用的重建算法无关。根据作者的研究结果，提出了基于位移的面元方法，更好的重建算法，和均匀投影角度视图的采集是提高胸部4D-CBCT图像质量的最重要因素。鉴于基于位移的分箱的实际问题以及投影角间距目前无法直接控制的事实，开发更好的重建算法是现阶段改善IGRT应用胸部4D-CBCT图像质量的最有效策略。(c)2014年美国医学物理学家协会。
Purpose: Respiratory signal, binning method, and reconstruction algorithm are three major controllable factors affecting image quality in thoracic 4D cone-beam CT (4D-CBCT), which is widely used in image guided radiotherapy (IGRT). Previous studies have investigated each of these factors individually, but no integrated sensitivity analysis has been performed. In addition, projection angular spacing is also a key factor in reconstruction, but how it affects image quality is not obvious. An investigation of the impacts of these four factors on image quality can help determine the most effective strategy in improving 4D-CBCT for IGRT.Methods: Fourteen 4D-CBCT patient projection datasets with various respiratory motion features were reconstructed with the following controllable factors: (i) respiratory signal (real-time position management, projection image intensity analysis, or fiducial marker tracking), (ii) binning method (phase, displacement, or equal-projection-density displacement binning), and (iii) reconstruction algorithm [Feldkamp-Davis-Kress (FDK), McKinnon-Bates (MKB), or adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS)]. The image quality was quantified using signal-to-noise ratio (SNR), contrast-to-noise ratio, and edge-response width in order to assess noise/streaking and blur. The SNR values were also analyzed with respect to the maximum, mean, and root-meansquared-error (RMSE) projection angular spacing to investigate how projection angular spacing affects image quality.Results: The choice of respiratory signals was found to have no significant impact on image quality. Displacement-based binning was found to be less prone to motion artifacts compared to phase binning in more than half of the cases, but was shown to suffer from large interbin image quality variation and large projection angular gaps. Both MKB and ASD-POCS resulted in noticeably improved image quality almost 100% of the time relative to FDK. In addition, SNR values were found to increase with decreasing RMSE values of projection angular gaps with strong correlations (r approximate to -0.7) regardless of the reconstruction algorithm used.Conclusions: Based on the authors' results, displacement-based binning methods, better reconstruction algorithms, and the acquisition of even projection angular views are the most important factors to consider for improving thoracic 4D-CBCT image quality. In view of the practical issues with displacement-based binning and the fact that projection angular spacing is not currently directly controllable, development of better reconstruction algorithms represents the most effective strategy for improving image quality in thoracic 4D-CBCT for IGRT applications at the current stage. (c) 2014 American Association of Physicists in Medicine.